Move over myelin

Although it is well established that autoreactive lymphocytes induce demyelination in multiple sclerosis, the exact antigenic targets that initiate disease are undefined. Planas et al. studied CD4+ T cells from the cerebrospinal fluid of patients with multiple sclerosis. One CD4+ T cell clone was reactive to the human enzyme GDP-l-fucose synthase; T cells from other patients were then identified, as well as myelin-reactive cells. Intriguingly, some of the GDP-l-fucose synthase–reactive cells could also be stimulated by a bacterial version of the enzyme. These tantalizing results identify a new autoantigen and suggest that one possible trigger of disease could be cross-reactivity to microbiota-derived peptides.